Immunocytochemical Localization of Thioredoxins in the Cyanobacteria Anabaena cylindrica and Anabaena variabilis

Summary: Colloidal gold conjugated goat anti-rabbit IgG and specific antisera raised against purified thioredoxins from Anabaena cylindrica and Anabaena variabilis have been used to determine the localization of thioredoxin in whole filaments of A. cylindrica and A. variabilis. Vegetative cells of A. cylindrica were labelled differently when tested with either of the two anti-thioredoxin sera. The anti-A. cylindrica thioredoxin serum reacted only with A. cylindrica thioredoxin which was located predominantly in the nucleoplasm in vegetative cells; it showed no association with the chromatoplasm. Anti-A. variabilis thioredoxin serum labelled vegetative cells of A. variabilis, particularly in the vicinity of the thylakoid membranes and also labelled A. cylindrica in the vicinity of the thylakoid membranes, indicating that a second thioredoxin or thioredoxin-like protein was present in this cyanobacterium. Heterocysts of A. cylindrica and A. variabilis showed substantially less labelling than vegetative cells when tested with both antisera.